Package structure of electric storage cells

ABSTRACT

A cell binder includes a frame body and a frame body. A storage portion of a electric storage cell are pressed/clamped by the bottom of an accommodating portion of the frame body and the bottom of an accommodating portion of the frame body. Also, a sealing portion of the electric storage cell is accommodated in a gap between the bottom of a fitting concave portion of the frame body  16  and the front end of a projecting portion of the other frame body, in a state of being deflected by bending, and the sealing portion is clamped between an inner wall of the fitting concave portion and an outer wall of the projecting portion, thereby fitting the frame bodies to each other. This makes it possible to reduce the size for clamping the sealing portion and to achieve the downsizing of the entire package. In addition, providing the sealing portion with deflections allows movements of the electric storage cell to be accommodated when vibrations are applied. This eliminates a possibility that the sealing portion will be damaged by a shearing stress, and leads to durability to be improved.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This is a U.S. national phase application under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/JP2005/021569 filed Nov. 24,2005 and claims the benefit of Japanese Application No. 2004-341249filed Nov. 25, 2004, The International Application was published inJapanese on Jun. 1, 2006 as International Publication No. WO/2006/057291A1 under PCT Article 21(2), the content of both applications areincorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a package structure of electric storagecells, the package structure increasing the shock resistance of theelectric storage cells while downsizing the package.

BACKGROUND ART

In recent years, flat electric storage cells having a substantiallyrectangular planar shape, such as a lithium ion secondary battery or anelectric double layer capacitor, have been put to practical use, and areregarded as promising as a power source for various equipment because oftheir high energy density, miniaturizability, easy maintenance, and thelike.

Such planar electric storage cells are often used as an assembled cellthat is packaged by laminating a plurality of the electric storagecells. When the electric storage cells are installed on a hybridelectric vehicle, an electric vehicle, or the like as a power source, itis necessary to ensure their durability to withstand vibrations.

For example, Japanese Unexamined Patent Application Publication No.2003-157813 discloses a technique for increasing the vibration-isolationeffect of an assembled cell by preventing an external case that is asupport member for unit cells from reaching a resonance point in a realusage region, by shifting a natural frequency of the assembled cell tothe higher frequency side.

When the planar electric storage cells are packaged, there is a casewhere individual electric storage cells are each accommodated in a framebody, and a plurality of the frame bodies each having accommodated theelectric storage cell is constituted as an assembled cell. In this case,in accommodating the planar cell into the frame body, it is possible toadopt, for example, a structure wherein one frame body is divided intotwo members, and after the two members have been opposed to each other,a storage portion of the electric storage cell and a sealing portion areclamped by pressing them planarly.

However, in such a structure in which all electric storage cells areplanarly fixed, the size of the package increases by a space for fixingthe sealing portion, and in addition, there is a possibility that thestorage portion with a relatively large weight and the sealing portionwith a relatively light weight will move at mutually differentfrequencies or amplitudes from each other, so that a stress mightconcentrate on the boundary portion between the storage portion and thesealing portion, resulting in a reduced durability. In particular, whenthe thickness of the storage portion and that of the sealing portionvary due to dimension deviations among individual electric storagecells, it is impossible to clamp the storage portion and the sealingportion by simultaneously pressing them, leading to a reduction in shockresistance.

The present invention has been made in view of the above-describedcircumstances. The object of the present invention is to provide apackage structure of electric storage cells, the package structure beingcapable of increasing the shock resistance of the electric storage cellswhile downsizing the package.

SUMMARY OF INVENTION

To solve the above-described object, the present invention provides apackage structure of electric storage cells, the package structure beingpackaged by accommodating the planar-shaped electric storage cells eachof which has a storage portion and a sealing portion that seals thestorage portion extendedly arranged around the storage portion in framebodies, the package structure including a first frame body for pressingthe storage portion from one surface side thereof; a second frame bodyopposed to the first frame body for pressing the storage portion fromthe other surface side thereof; and a holding structure is provided inthe first frame body and the second frame body, the holding structurebeing for accommodating the sealing portion in a deflected state andbeing fit in the pressing direction of the storage portion in a statewhere the ends of the sealing portion are clamped. Here, the holdingstructure can be constituted by a gap for accommodating the sealingportion in a bent state, and wall surface portions being fit in thepressing direction of the storage portion in a state where the ends ofthe sealing portion are clamped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a storage capacitor package.

FIG. 2 is a perspective view of electric storage cells connected inseries.

FIG. 3 is a sectional view taken along a line A-A of FIG. 1.

FIG. 4 is diagram showing a clamping state when a sealing portion islonger than a standard size.

FIG. 5 is diagram showing a clamping state when the sealing portion isshorter than the standard size.

FIG. 6 is a diagram showing another holding structure of the electricstorage cell.

FIG. 7 is a diagram showing still another holding structure of theelectric storage cell.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings. FIGS. 1 to 7 concern theembodiment of the present invention. Here, FIG. 1 is a perspective viewof a storage capacitor package; FIG. 2 is a perspective view of electricstorage cells connected in series; FIG. 3 is a sectional view takenalong a line A-A of FIG. 1; FIG. 4 is diagram showing a clamping statewhen a sealing portion is longer than a standard size; FIG. 5 is diagramshowing a clamping state when the sealing portion is shorter than thestandard size; FIG. 6 is a diagram showing another holding structure ofthe electric storage cell; and FIG. 7 is a diagram showing still anotherholding structure of the electric storage cell.

In FIG. 1, reference numeral 1 denotes a storage capacitor package usedas power source unit, for example, in an electric vehicle (EV) or ahybrid electric vehicle (HEV). This storage capacitor package 1 ismainly composed of a plurality (in the illustrated example, five pieces)of flat electric storage cells 5 (refer to FIG. 2) with a substantiallyrectangular planar shape, and an external case 2 for accommodating theelectric storage cells 5. The external case 2 is constituted, forexample, by laminating a plurality (in the illustrated example, fivepieces) of cell binders 15 each constituted of a resin-made flat framebody with a substantially rectangular planar shape.

The electric storage cell 5 is a flat storage capacitor having asubstantially rectangular planar shape, such as a lithium ion secondarybattery or an electric double layer capacitor. As typified by a planarlaminate type lithium ion secondary battery, the electric storage cells5 are ones configured by enclosing and sealing a laminated body ofinternal electrodes and an electrolytic layer, for example, by asheet-shaped laminated film formed by insulation-coating the surface ofan aluminum-base metal layer with a resin layer.

That is, as shown in FIG. 2, the electric storage cells 5 each include arectangular-shaped storage portion 6 that embraces a storage elementcomprising the laminated body of the electrolytic layer and theelectrodes, and that is formed somewhat thicker than peripheries; asealing portion 7 extendedly arranged in a sheet shape around thestorage portion 6; and two metal tabs 8 and 9 that serve as positive andnegative electrode terminals, respectively, and that are exposed fromboth ends of the sealing portion 7. In this embodiment, the electricstorage cells 5 are serially connected in advance by terminalconnections of the tabs 8 and 9. A cell string 5A is formed by theseserially connected electric storage cells, and accommodated in theexternal case 2 in a state of being arranged in a staggeredconfiguration.

Hereinafter, for convenience, the direction in which the tabs 8 and 9 ofthe electric storage cell 5 are extended is referred to as alongitudinal direction, and the direction orthogonal to the direction inwhich the tabs 8 and 9 of the electric storage cells 5 are extended isreferred to as a lateral direction, as appropriate.

The cell binder 15 comprises a frame body 16 serving as a first framebody and a frame body 17 serving as a second frame body, and theelectric storage cell 5 is accommodated between the one set of framebodies 16 and 17. In such the cell binder 15, the frame body 16 of anarbitrary cell binder 15 and the frame body 17 of the other cell binder15 abut against each other, and are connected by a fitting structureprovided at four corner of the abutting surface.

In one abutting surface of a frame body 17 as shown in FIG. 1, twocylindrical pins 10 are installed in upright positions in the laminatingdirection, at both corners on the side where the tabs 8 and 9 areextended and exposed. Also, on the other side where the tab 9 of theelectric storage cell 5 is extended and exposed, there are provided twoholes 11 into which the pins 10 (i.e., the pins 10 of the other cellbinder 15) are to be fitted. The pins 10 and the holes 11 are providedalso to an abutting surface of the other abutting surface of the framebody 17, while they are not shown. Here, the pins 10 and holes 11 aredisposed so that the positional relationship of the pins 10 with theholes 11 becomes reverse between the frame body 17 and the frame body16.

That is, the pins 10 and the holes 11 of the frame body 17 of apredetermined cell binder 15, respectively, are fitted to the holes 11and the pins 10 of the frame body 16 of the other cell binder 15,whereby the cell binders 15 are fitted and connected to each other. Inthis case, a plurality of locking grooves 10 a is provided in the outerperipheral surface of each of the pins 10. These locking grooves 10 aimplement a retaining function with a predetermined strength (so-calleda semi-lock structure) between the pin 10 and the hole 11 to be fittedthereto.

The electric storage cell 5 accommodated in the cell binder 15 is heldby fitting of the frame bodies 16 and 17 in the laminating direction.The holding structure of the electric storage cell 5 by the frame bodies16 and 17 constitutes a dual holding structure composed of a structurefor clamping the storage portion 6 serving as a cell body being pressedby the frame bodies 16 and 17 in the laminating direction, and astructure for fitting in the pressing direction (laminating direction)of the storage portion 6 in a state where the sealing portion 7 on bothlateral sides of the storage portion 6 are bent and the ends thereof areclamped by the frame bodies 16 and 17.

Specifically, as shown in FIG. 3, which is a sectional view taken alongthe lateral line A-A in FIG. 1, on the side of the frame body 16 to befitted oppositely to the frame body 17, a substantiallyrectangular-shaped accommodating portion 16 a with a bottom is openedfor accommodating one surface side of the storage portion 6 of theelectric storage cell 5. On both lateral sides of this accommodatingportion 16 a, there are provided groove-shaped fitting concave portions16 b each having a predetermined depth in the laminating direction and alength larger than the width in the longitudinal direction of thesealing portion 7. An inner wall (wall portion) 16 c on the lateraloutside of the fitting concave portion 16 b is flush with an inner wall(wall surface portion) of a projecting portion 16 d that forms a lateralframe portion of the frame body 16 and that is projected from theopening top surface of the accommodating portion 16 a, and as will bedescribed below, this inner wall 16 c is set so as to clamp the sealingportion 7 of the electric storage cell 5, in conjunction with the framebody 17.

On the other hand, on the side of the frame body 17 to be fittedoppositely to the frame body 16, a substantially rectangular-shapedaccommodating portion 17 a with a bottom is opened for accommodating theother surface side of the storage portion 6 of the electric storage cell5. On both lateral sides of the accommodating portion 17 a, there areprovided projecting portions 17 b each having an elongated shape in thelongitudinal direction and a predetermined projection height in thelaminating direction. The projecting portion 17 b is formed into asubstantially arcuate shape in the projection front end thereof. Anouter wall (wall portion) 17 c on the lateral outside of the projectingportion 17 b reaches the substantially flush level with the bottomsurface of the accommodating portion 17 a, and connected to a stepportion against which the front end surface of the projecting portion 16d of the frame body 16 abuts.

As a holding structure for the sealing portion 7 of the electric storagecell 5, the cell binder 15 with the above-described arrangement adopts astructure in which the frame bodies 16 and 17 are fitted to each otherwhile clamping the sealing portion 7 of the electric storage cell 5between the inner wall 16 c on the lateral outside of the fittingconcave portion 16 b of the frame body 16 and the outer wall 17 c on thelateral outside of the projecting portion 17 b of the frame body 17.Thereby, the present holding structure constitutes a wall portion thatis capable of fitting the frame bodies 16 and 17 to each other in thepressing direction of the storage portion 6 in a state where the ends ofthe sealing portion 7 of the electric storage cell 5 are clamped. Atthis time, the holding structure is set so that a gap is formed betweenthe bottom of the fitting concave portion 16 b and the front end of theprojecting portion 17 b. In this gap, the sealing portion 7 of theelectric storage cell 5 is accommodated in a state of being deflected bybending.

Also, in a holding structure for the storage portion 6 of the electricstorage cell 5, the depth of the each of the accommodating portions 16 aand 17 a is set so that, when the front end surface of the projectingportion 16 d of the frame body 16 abuts against the step portion outsidethe projecting portion 17 b of the frame body 17, the storage portion 6of the electric storage cell 5 can be pressed/clamped by the bottom ofthe accommodating portion 16 a of the frame body 16 and that of theaccommodating portion 17 a of the frame body 17. Furthermore, thisholding structure is set so that, when the front end surface of theprojecting portion 16 d of the frame body 16 abuts against the stepportion outside the projecting portion 17 b of the frame body 17, theside edge of the accommodating portion 16 a of the frame body 16 andthat of the accommodating portion 17 a of the frame body 17 are opposedto each other with a predetermined distance therebetween so as not topress the base portion of the sealing portion 7.

As a result, a lateral dimension D for clamping the sealing portion 7can be made small as compared with that in a structure in which thesealing portion 7 is planarly clamped, thereby allowing the entirepackage to be downsized. In addition, providing the sealing portion 7with deflections allows movements of the electric storage cell 5 to beaccommodated when vibrations are applied in the lateral direction (i.e.,direction orthogonal to the laminating direction). This eliminates apossibility that the sealing portion 7 will be damaged by a shearingstress, and leads to durability to be improved.

Moreover, by adopting the structure for clamping the sealing portion 7of the electric storage cell 5 by providing the sealing portion 7 withdeflections, it is possible to accommodate a variation in the laterallength of the sealing portion 7 of each individual electric storage cell5. That is, even if there occurs a dimension error of the sealingportion 7 of the electric storage cell 5 relative to a standard value,there is no need to increase the dimension D of the cell binder 15 inresponse to the dimension error, but one can address the variation usingthe cell binder 15 of the unchanged dimension.

For example, as shown in FIG. 4, if the width of the sealing portion 7of the electric storage cell 5 has a plus error relative to the standardvalue, then, making longer the bending length of the sealing portion 7to be accommodated in the gap between the bottom of the fitting concaveportion 16 b of the frame body 16 and the front end of the projectingportion 17 b of the frame body 17 than an ordinary bending length, makesit possible to keep proper the length of the sealing portion 7 to beclamped between the inner wall 16 c of the fitting concave portion 16 band the outer wall 17 c of the projecting portion 17 b, and to avoidmalfunctions such as running-over of the sealing portion 7 to theoutside by accommodating the plus error.

On the other hand, as shown in FIG. 5, if the width of the sealingportion 7 of the electric storage cell 5 has a minus error relative tothe standard value, then, making shorter the bending length of thesealing portion 7 to be accommodated in the gap between the bottom ofthe fitting concave portion 16 b and the front end of the projectingportion 17 b than the ordinary bending length, makes it possible toensure the length of the sealing portion 7 to be clamped between theinner wall 16 c of the fitting concave portion 16 b and the outer wall17 c of the projecting portion 17 b, and to reliably hold the sealingportion 7.

In a structure in which the storage portion 6 and the sealing portion 7are clamped by mutually different surfaces in the same direction(laminating direction), if the storage portion 6 varies in thethickness, there is a possibility that only one of the storage portion 6and the sealing portion 7 can be pressed/clamped. However, the holdingstructure in this embodiment has an independent structure in which thestorage portion 6 and the sealing portion 7 are pressed/clamped inmutually different directions, and therefore, even if the storageportion 6 varies in the thickness, it is possible to simultaneouslyclamp the storage portion 6 and the sealing portion 7, and to ensure astable characteristic against vibrations during service by accuratelyproviding a bearing stress to the storage portion 6.

Furthermore, the frame bodies 16 and 17 constituting the cell binder 15have the structure to fit to each other, and hence, when a plurality ofcell binders 15 is laminated by accommodating the electric storage cells5 between the frame bodies 16 and 17, there is no possibility that thecell binders 15 will laterally deviate from each other. As aconsequence, the assembling work of the storage capacitor package 1 isimproved, thereby allowing productivity to be enhanced.

The above-described holding structure of the electric storage cell 5 canalso be made a simplified structure shown in FIG. 6 or FIG. 7. That is,it is possible to form a dual holding structure composed of a structurefor clamping the storage portion 6 serving as the cell body in thelaminating direction as in the case of the cell binder 15, and astructure for clamping the sealing portion 7 in the directionsubstantially orthogonal to the laminating direction by bending thesealing portion 7.

A cell binder 20 shown in FIG. 6 is fundamentally the same as the cellbinder 15 in the holding structure of the electric storage cell 5, butthe cell binder 20 is low in the bending amount of the sealing portion 7compared with the cell binder 15. The cell binder 20 comprises a framebody 21 serving as a first frame body that is made more shallow in thefitting concave portion 16 b of the frame body 16, and a frame body 22serving as a second frame body, the frame body 22 being to be fitted tothe frame body 21.

That is, the frame body 21 includes a substantially rectangular-shapedaccommodating portion 21 a with a bottom for accommodating one surfaceside of the storage portion 6 of the electric storage cell 5;taper-shaped guide portions 21 b that are provided on both sides of theaccommodating portion 21 a and that are diverged from the opening topsurface of the accommodating portion 21 a toward the laminatingdirection; and a side wall portion (wall surface portion) 21 c that isprojected from the guide portion 21 b toward the laminating direction tothereby form lateral frame portion of the frame body 21. On the otherhand, the frame body 22 includes a substantially rectangular-shapedaccommodating portion 22 a with a bottom for accommodating the othersurface side of the storage portion 6 of the electric storage cell 5;taper-shaped guide portions 22 b that are provided on both sides of theaccommodating portion 22 a and that are oppositely arranged so as toform a predetermined gap with respect to the guide portion 21 b of theframe body 21; and a side wall portion (wall surface portion) 22 cformed on the lateral outside of the guide portion 22 b.

The cell binder 20 accommodates the storage portion 6 of the electricstorage cell 5 in the accommodating portion 21 a of the frame body 21and the accommodating portion 22 a of the frame body 22, and furtheraccommodates the sealing portion 7 of the electric storage cell 5 in agap between the guide portion 22 b of the frame body 21 and the guideportion 22 b of the frame body 22, in a state of being provided withdeflections by bending in the laminating direction. The ends of thesealing portion 7 are each clamped between the inner wall surface of theside wall portion 21 c of the frame body 21 and the outer wall surfaceof the side wall portion 22 c of the frame body 22, thereby fitting theframe bodies 21 and 22 to each other.

Compared with the case of the cell binder 20 in FIG. 6, in a cell binder25 shown in FIG. 7, the area for accommodating the sealing portion 7 ofthe electric storage cell 5 is arcuately shaped. In the cell binder 25,the guide portions 21 b and 22 b are each arcuately shaped. The cellbinder 25 accommodates the storage portion 6 of the electric storagecell 5 in an accommodating portion 26 a of a frame body 26 serving as afirst frame body, and an accommodating portion 27 a of a frame body 27serving as a second frame body, and further accommodates the sealingportion 7 of the electric storage cell 5 in a gap formed between anarcuate guide portion 26 b of the frame body 26 and an arcuate guideportion 27 b of the frame body 27, in a state of being provided withdeflections by being arcuately bent in the laminating direction. Theends of the sealing portion 7 are each clamped between the inner wallsurface of a side wall portion (wall surface portion) 26 c of the framebody 26 and the outer wall surface of a side wall portion (wall surfaceportion) 27 c of the frame body 27, thereby fitting the frame bodies 26and 27 to each other.

In these cell binders 20 and 25, the bending amount of the sealingportion 7 of the electric storage cell 5 is low. Therefore, as comparedwith the cell binder 15, the cell binders 20 and 25 are somewhat smallin the degree of tolerance for dimension error of the sealing portion 7,but can reduce the load upon the sealing portion 7.

As described above, the package structure of electric storage cellsaccording to this embodiment is not a structure in which the storageportion 6 of the electric storage cell 5 and the sealing portion 7 areplanarly pressed/clamped in the same direction (laminating direction),but a structure in which the storage portion 6 is pressed/clamped in thelaminating direction, and in which the ends of the sealing portion 7 areeach pressed/clamped by the wall surfaces in the direction substantiallyorthogonal to the laminating direction in a state where the sealingportion 7 is provided with deflections. This makes it possible toincrease the shock resistance of the electric storage cells 5 whiledownsizing the package.

1. A package structure of electric storage cells, the package structurebeing packaged by accommodating the planar-shaped electric storage cellseach of which has a storage portion and a sealing portion that seals thestorage portion extendedly arranged around the storage portion in framebodies, the package structure comprising: a first frame body forpressing the storage portion from one surface side thereof; a secondframe body opposed to the first frame body for pressing the storageportion from the other surface side thereof; wherein a holding structureis provided in the first frame body and the second frame body, theholding structure being for accommodating the sealing portion in adeflected state and being fit in the pressing direction of the storageportion in a state where the ends of the sealing portion are clamped. 2.The package structure of electric storage cells according to claim 1,wherein the holding structure comprises a gap for accommodating thesealing portion in a bent state, and wall surface portions being fit inthe pressing direction of the storage portion in a state where the endsof the sealing portion are clamped.